Been getting non stop rain here and still have lots of other valleys to go through on family issues, so may as well know the answer to questions that I will eventually come to. My car has a (I am sure it is garbage) M-20 in it that I am definitely swapping the M-21 into and it currently has a 1972 8.5 rear end in it. In addition to the M-21 I will be putting a factory geared “ON” coded 8.2 3:64 Posi in the car. Anyone know if this will cause any driveshaft length or yoke issues & what parts I will need if so? Haven’t been on regularly but Thank You in advance for any help. Fritz
Sorry Fritzee, but 72/72 same style driveshafts will be 0.86 inch (app 7/8") shorter than 68-70 cars according to TSB 71-I-5A.
Thank you Frank and Steve! Yep, that woke me up the other night as an "what if". My car came from the factory as a 72-GS-350 automatic and I believe the previous owner made the conversion with the compatible to manual trans, Turbo 350 crossmember and I am guessing the factory 72 small block car drive shaft & the stock 8.5. I have never had a driveshaft modified but would a 70-350 or 455 driveshaft work okay so I can use the 8.2 rear? Thank you again for taking the time to share your knowledge .
You need one of these Fritzensticker... I went from the three speed to a ST-10 and the fit was perfect with the 8.2. Stock 3 speed crossmember etc. You're reengineering something 50 years old. Theres no positive answer unless youve got $$$ to blow. You may need to change the style of rear U-joint. ws
I have seen these evil measuring sticks before Captain. Bill, but we are not friends. I still have about a $400 stack of custom storm windows I checked & checked the size of with an EMS (Evil measuring stick) for this 1890 farm house that none appear to fit the original or multi sized “modern” (1970’s) windows added by previous owner. Well, another depressing set back, but at least I know now. So much more difficult than back in the day when I bought my GS’s that I could afford that actually ran and drove and then I “just” maintained them. I know it is my fault that I am trying to as close as possible make a 72 into my forever 1970 GSX dream car but it is my only chance with all the cards stacked against me. Should have listened to my sister “You have no business with a car like that,those are only for rich people who can afford them!”. That just pissed the rebel in me off though (never tell me I cannot do something!) but looking like she is winning this argument,soooo much to do on this “car” & the wreck in our van (unlicensed guy rear ended us at dead stop doing over 40mph) has really amped up my previous untreated injuries but I have still been swinging & slinging but crap like this with custom parts needed that I can’t barter around for like stock parts might finally torpedo my dream. With all the hate in the world,and good friends dying off,and many of those left being on attack mode over nearly anything the dream is looking more like a nightmare anyway. Isn’t going to take much more for me just to say the hell with it,it was a good run but DAMN! Oh well, I have a mountain of other negative crap not car related I have to deal with demanding continued attention, not like the car ever completed would give me my youth back but just wanted something of my own (a BUICK) to give me a smile but guess that was asking WAY too much! Anyhow thanks for letting me know the fix,I know my brain will keep working on a solution I can afford just really depressed right now.
Baby Steps, Fritz... baby steps. Is the motor and trans in the frame along with the differential? Slip a DS with a front yoke into the trans and see whats there. I was lucky when I did the '64. Pulled the V6 and 3 speed out, installed an empty block and 4 speed which measured 1-1/2" too long in the tail shaft. Had a new joint installed in the front and the rear slipped right in where it belonged. Popped it out and did the rear. I was prepared to cut the shaft since the EMS told me to, but the eyes dont lie. YOU CAN NOT just take anyone's word that "this is what you need". With as much dickin' around as has been done to the PMTX (poor mans touring X), you may just find some stupid dodge DS will fit (minus the U joint equation). Take it to the manicurist for an epoxy nail clear coat and youll be good to go; honest. Get that puppy going woodja? Youd be surprised that "rowing the gears" dream consists of a hole shot here and there, maybe a mash on the stomper pedal, or just a million thumbs up. Cruising and blasting around town with the babes aint gonna happen. Back whenever, these guys were daily drivers. Every weekend I spent making a 250 mile trip to see my dad. Cruisin'? Hell yeah. Now we get to cruise in our memories. After an hour or two of "rowing" around town, Im ready for coffee and a siesta LOL Better watch it my friend, pretty soon we'll be rowing the boat under that rainbow bridge! ws
You'll also have to check the input and output shafts of the M20 vs M21..... Input shaft could be 10 spline or 26 spline, output could be 27 or 32 spline!
That you Billingsly and Thank You Walt for catching that on the M-20 to M-21. I will tell you one HUGE thing this car has done,even though “I thought” (Yeh! My BEST thinking got me in this project! Not real encouraging in my thinking dept! Lol) but this car has humbled me even further! I absolutely hate to ask what should be simple issues on this car after over 45 years of turning wrenches, but in fairness that was on pretty complex textile & laboratory equipment (no “walk in the park” as we reconditioned whatever came out of our trucks so zero consistency) and back “in my day” well, my GS’s just frankly ran. There were the common repairs and yes some occasional big drivetrain repairs but nothing like this! Basically I feel like a huge green horn & whatever “I use to know” well.....you know (orrrr dooooo you? Lol). Anyhow biggest issues have been identified thanks to y’all and THAT is the biggest part because I can’t afford guessing, so Thank You for readjusting my crosshairs to the targets. I am trying to build the “Poor Touring Car” just as I would have checked the boxes off in 1970 with rough but correct 1970 GM GSX parts and to find this 3:64 8.2 was VERY exciting. Sorry for the whining around earlier (“Want some cheese with that WHINE, Fritzenblabbin?!!”) I’ll keep plugging along and enhancing my humility at the same time! Thanks again. Kindest Regards, FritzenwillBshiftin! Last motor progress b4 Mom fell,Father in Law put in Hospice & pain from the wreck over took me. AIN’T GIVING UP YET THOUGH!
Dont give up the ship Fritzenbanger! Tell me the trick about putting that lower center header bolt in on the passenger side. The other day while cruising around, I saw a Camaro in this guys shop that was up on 16x16x12" tall blocks, built from 2x4's under each tire. Almost enough room to crawl under on the hands and knees. Way better than ramps even. Ever think about one of those harbor fright canopies to work out of the weather/sun? That way youll lose that "dred" of getting out there for some under-graduate studying LOL... ws Walt... how far from Lansdale are you? Have a pal from there... ws
Just for kicks... ws https://madison.craigslist.org/pts/d/barneveld-70-gto-and-misc-body-parts/7125607099.html
Almost forgot about the question on the M/T center bolt. I crammed a piece of rag in the 1/4” drive socket so the header bolt was stuck and didn’t end up falling down on top of the tube jungle for me to fish out. Obviously used an extension & with patience (and drift pins) managed to catch a couple of threads. Then tightened & loosened the other header bolts (more drift pinning on feisty ones) until the middle hole was perfectly lined up. Then I was able to reach my middle fingers in from both sides of the tubes to the center bolt and finger tighten those suckers way in & finished with either the ratchet or box end ratcheting wrench (can’t remember which one) did ALL of it without a lift but used two floor jacks (one on a$$ end of header to help in aligning holes since working alone) and other to take lots of weight off of the jack stands. Took a bunch of breaks and a couple of walks away from it to think but was one of my easiest header installs which I was VERY happy about. Even Rosie seemed semi impressed......
Yeah... I used the 12 point header bolts and a myriad of other sockets etc. The best thing I found was a 12 point 3/8" box wrench and with 1/24 (!) of a turn at a time, I managed to catch a thread and went with it. Glad the holes were tapped clean and never seized the bolts! Bar none, one of the worst jobs on these cars! HINT... I use spray glue on that stuff too! Dont spare it LOL... I was linking that CL ad just to show you drive shafts are available. Its a hunt and peck deal. ws
Yes, I just need to confirm the splines on the Muncie and driveshaft length and what yoke I need first before I go CL shopping. Been rainin like mad down here so I am outta commission on car stuff anyway & hospice called today & said my wife’s Dad is “getting very close “ : ( “anytime”. Going to really miss that gentleman .
Sorry to hear that Fritz ;-(( That canopy would work but then HURRICANE season starts in another 4 days... ws
Bill, I'm close to Lansdale, about 10 miles away. I'm near Lake Galena. Fritz, check the length of that M21 too....I sorta recalled a length difference and this article confirms it: https://www.chevydiy.com/muncie-4-speed-the-complete-history/ A longer M21 and a shorter 8.2 might work out for you!
Thanks Walt, that would be awesome if the length & splines work out! On my to due list whenever the monsoons stop around here. Yes Bill, a Harbor Freight canopy wouldn’t make it through one storm or high winds we have been getting around here. Someone would probably find it in South Carolina the next day heh heh
